Multicast aided cooperative beamforming wireless system

ABSTRACT

A cooperative wireless system using a multicast protocol to facilitate coordinating coherent addition and subtraction of wireless signaling or other beams originating from a plurality of antenna units at a target location is contemplated. The system may utilize multicast-based regulation and distribution of transmission control parameters necessary for the antenna units to synchronize the wireless signaling in a manner sufficient to enable the coherent addition and subtraction thereof at the target location.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/443,949, filed Jun. 18, 2019, which application is a continuation ofU.S. application Ser. No. 16/032,929, filed Jul. 11, 2018, which in turnclaims the benefit of U.S. provisional Application No. 62/531,503 filedJul. 12, 2017, the disclosure of which is incorporated in its entiretyby reference herein.

TECHNICAL FIELD

The present invention relates to multicast aided wireless signalingsystems, such as but not necessary limited to wireless signaling systemsincluding a plurality of spatially separated remote antenna units havingcapabilities sufficient to facilitate coordinating beamforming orotherwise directing wireless signaling to a target location whereatsignaling from multiple antenna units may be coherently added.

BACKGROUND

Increasing demand for capacity has led to deployment of denselydistributed wireless networks, e.g. non-cellular, cellular and/ormixed-use networks. Flexible provisioning of capacity to targetedlocations can be realized by coordinating transmission of the samesignal from multiple locations using different beams so that thesesignals can add in phase at a target location to produce an effectivesignal having a greater signal-to-noise ratio and improved capacity thanthe individual beams could provide independently. The number of antennasdeployed with beamforming capabilities suitable for this approach mayincrease in the future such that a need is recognized for a system thatcan manage the attendant resources in a flexible and agile manner. Onenon-limiting aspect of the present invention contemplates addressingthis future need with a multicast aided cooperative beamforming wirelesssystem having capabilities sufficient to facilitate the complex messagedelivery and signaling synchronization necessary to enable coherentaddition and subtraction of wireless signaling at a target location whenthe corresponding wireless signaling originates from multiple remoteantenna units, which may optionally be spatially separated across ageographical area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a communication system in accordance with onenon-limiting aspect of the present invention.

FIG. 2 illustrates a multicast protocol in accordance with onenon-limiting aspect of the present invention to facilitate multicastaided coordination.

FIG. 3 illustrates a flowchart of a method for synchronizing wirelesssignaling in accordance with one non-limiting aspect of the presentinvention

FIG. 4 illustrates a ranging process in accordance with one non-limitingaspect of the present invention.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

FIG. 1 illustrates a communication system 10 in accordance with onenon-limiting aspect of the present invention. The system 10 may beconfigured to facilitate electronic signaling between a signalprocessor/headend/hub 12 and premise equipment (CPE), user equipment(UE), access points (APs), terminals or other devices, which may becollectively referred to as end stations (ESs). The signal processor 12may be configured to facilitate transport of virtually any type ofsignaling, including signaling associated with a multiple systemoperator (MSO), such as but not necessarily limited to a cable,satellite, or broadcast television service provider, a cellular serviceprovider, and high-speed data service provider, an Internet serviceprovider (ISP), etc. The end stations may correspond with anyelectronically operable device having capabilities sufficient tofacilitate directly or indirectly interfacing a user with signalingtransported through the communication system 10. The end stations may bea gateway, a router, a computer, a mobile phone, a cellular phone, amedia terminal adapter (MTA), a voice over Internet protocol (VoIP)enabled device, a television, a set top box (STB), network addresstranslator (NAT), etc.

The present invention contemplates distinguishing between wireless andwireline communications for explanatory purposes. The wirelinecommunications may correspond with any type of electronic signalexchange where a wire, a coaxial cable, a fiber or other bound medium isused to facilitate or otherwise direct at least a portion of the relatedsignaling. The wireline communications include but are not necessarilylimited to those carried at least partially over a fiber/cable backboneassociated with a cable television distribution system, commonlyreferred to as a hybrid fiber coaxial (HFC) system, or an Internet ornon-Internet based data communication system. The wirelesscommunications may correspond with any type of electronic signalexchange where an antenna, antenna port or other transmitting type ofdevice is used to communicate at least a portion of the signaling asradio frequency (RF) signals, such as over a wireless link or through anunbound or air medium. The wireless communications may include but arenot necessary limited to satellite communications, cellularcommunications (e.g., LTE) and Wi-Fi communications. The use of wirelineand wireless communications and the corresponding mediums are notintended to limit the present invention to any medium, protocol, orstandard and is instead noted to differentiate between two types ofcommunications, e.g., bound and unbound.

The signaling desired for transports through the communication system 10may be received at the signal processor 12 and thereafter carried by oneor more fibers to a fiber node from which a plurality of coaxial cablesmay facilitate further delivery to different geographical areas,optionally with use of splitters and/or amplifiers. The coaxial cablesare shown to include a plurality of taps (shown as rectangles) throughwhich various end stations may be connected to receive the wirelinesignaling and/or other signaling associated with the headend, e.g.,signaling associated with other types of content and/or datatransmissions. One non-limiting aspect of the present inventioncontemplates a plurality of remote antenna units being dispersed atgeographically spaced taps within the system to facilitate wirelesssignaling at a target location 14, which is shown for exemplary purposesto correspond with the location of an end station being targeted forcoherent communications. While the present invention is predominatelydescribed with respect to utilizing an HFC type of cable network, thepresent invention is not necessary so limited and fully contemplates itsuse and application in facilitating wireless signaling to a targetlocation irrespective of the communication medium utilized to providesignaling, information, data, etc. to the remote antenna units forsubsequent transport to the target location.

One non-limiting aspect of the present invention contemplates employingmultiple remote antenna units fed by the network to generate coordinatedbeams that coherently add over the target location, which is shown forexemplary purposes to correspond with three of the five available remoteantenna units actively coordinating beams to coherently add at thetarget location. A central coordination system 16 in the hub or headendlocation may be used to distribute information via the remote antennaunits to the target location by means of a collection of beams from thedifferent remote antenna units. A common timing reference available atthe hub or headend may be used to synchronize transmissions and addprecise delays to the transmissions traversing each of the remoteantenna units such that all signals arrive in phase at the target enddevice. The central coordination system may include a non-transitorycomputer-readable medium having a plurality of non-transitoryinstructions executable with a processor associated therewith tofacilitate generating control parameters required for controlling andsynchronizing the remote antenna units to provide coherent addition andsubtraction of wireless signaling. The transmission path distance to anend device through each remote antenna unit is typically different dueto the remote antenna units being unequally spaced relative to thetarget location, unequal distribution of interferences from othersignaling or objects, etc. A multi-antenna ranging process may beemployed to facilitate assessing the variability associated therewith toenable a coordinated process for synchronizing wireless signaling of theremote antenna units.

Initially, an end device may connect to the network through one of theplurality of remote antenna units available for communication therewith.To connect through one of the remote antenna units, an initial roughinitialization or authentication process may take place to avoid overlapbetween transmissions from other end devices, e.g., to designate one ofthe plurality of remote antenna units as a primary controller or initialor temporary interface to the end station. A more precise timing processor ranging process may take place when in-phase addition of two or moresignals is required, i.e., when a need or desirability arises tofacilitate coherent addition and/or subtraction of wireless signaling atthe target location for multiple remote antenna units. The remoteantenna units may have certain degree of intelligence, such as in theform of a computer-readable medium having a plurality of non-transitoryinstructions executable with a processor associated therewith, which mayallow them to detect downstream traffic intended for the end devicesbeing serviced. The remote antenna units detecting traffic to betransmitted therefrom may then parse control parameters included withinattendant messaging to decode the portions of the information requiredto adjust delay and amplitude, beam information, channel frequencies,etc. to facilitate communications with the target location.

A training signal may be distributed as part of the ranging process tofacilitate synchronizing signaling to the target location after the endstation is initially associated with one of the remote antenna units.The reception of the training signal from two remote antenna units maybe used to determine whether one of the remote antenna units, or thesignaling associated therewith, is lagging or is ahead in relation tothe other remote antenna units intended to facilitate coherent signalingwith the targeted end stations. Timing discrepancies, calculations orother factors derived from monitoring arrival of the test signals at thetargeted end station may then be used to facilitate determiningadjustments necessary to synchronize signal delivery in a mannersufficient for coherent addition and subtraction. The initial remoteantenna through which transmission was established may be used asreference for timing calibration purposes, which may be a remote antennaunit (RAU) referenced by the index “0”. The next antenna thatcontributes to the signal may be labeled with index 1, the next one withindex 2 and so on. The training signal that is sent in the downstream,i.e., from the signal processor to the remote antenna units, may includea header indicating the wireless end device ID to which the trainingsignal is targeted along with ranging parameters characterizing thetraining signal in the payload. In one embodiment, a payload with asinusoidal signal can be used.

This training signal payload can be divided in multiple synchronizationsegments depending on the number of additional remote antenna units thatcan potentially participate. Three segments may be used if three remoteantenna units in addition to the reference remote antenna unitparticipate. It may be the task of the remote antenna units identifiedwith indices higher than 0 to change the phase of their training signalsegment by 180° as it traverses the remote antenna unit. This way,assuming the amplitude has also been calibrated, the corresponding testsignal would be cancelled during the segment corresponding to theadditional remote antenna as it reaches the wireless end device. Thesegment duration is known such that the cancellation period would allowthe central coordination system to automatically determine when theprecise delay has been achieved, i.e., when ranging parametersassociated with the remote antenna units have been iteratively set tosufficiently cancel/subtract its test signal from a reference testsignal associated with the remote antenna unit having an index of 0. Dueto variability in the wireless environment it may be better to detect aminimum or complete cancellation rather than a maximum value, e.g.,rather than coherently adding the signaling to create the maximum value,a more definitive metric may be determined by coherentlysubtracting/canceling the test signals with the 180° phase shift.

The information gathered through the ranging process by the targeted endstation may be communicated to the central coordination system inresponse messages for purposes of calculating additional adjustments inamplitude and phase for the remote antenna units associated with eachsegment, i.e., the ranging parameters may be iteratively adjusted untilsuitable to facilitate coherent communications. This precise rangingprocess may be determined for each remote antenna that could contributein building the composite signal at the target location, such as whennew remote antenna units are added to the system through installation,power up or otherwise activated. The training header included inmessages sent to the remote antenna units as part of the ranging processmay contain information regarding which remote antenna unit(s) shouldintroduced the 180° shifted segment marker. Such ranging messages mayinclude specifically addressing a new remote antenna unit and/orperiodically requesting to verify participating remote antenna unit tomake sure that nothing has changed. It may take a few ranging iterationsuntil the phase and delay adjustment has been accurately obtained foreach of the remote antenna units, i.e., to determine the rangingparameters necessary for the remote antenna unit to perform the desiredcancellation at the target location. The central controller can requestthe adjustment for the next remote antenna unit (index 2) once the phaseand delay are fully compensated for the prior remote antenna unit(index 1) and then on to each remote antenna unit until all the rangingparameters for cancellation are determined. Other events such as asudden decrease in signal to noise ratio of the receiver or low biterror rate would also trigger ranging messages or re-instigation of theranging process.

At a conclusion of the ranging process when ranging parameters for eachof the plurality of remote antenna units available for communication tothe target location are determined, the central coordination system mayutilize those parameters to calculate control parameters for use infacilitating data, information or other non-ranging transmissions to thetarget location. One non-limiting aspect of the present inventioncontemplates facilitating such communications with the target locationusing multicast protocols to facilitate selecting one or more of theavailable plurality of remote antenna units for data delivery. Themulticast protocol may be used to determine which of the capable remoteantenna units to start contributing a beam towards the targeted enddevice. As signaling dynamics change or communication resources requireredistribution, the multicast protocol may be utilized to facilitatepruning and joining additional remote antenna units, optionallyre-instigating the ranging process to account for signaling influencesresulting from adding or removing the remote antenna units. Themulticast protocol may be characterized as a communication processwhereby multicast messages having a payload or other information desiredfor communication to the target end station may be transmitted in aone-to-many arrangement from the signaling processor to each of theplurality of antenna units and/or to one or more antenna units selectedto be members of the multicast group. The corresponding antenna unitsmay then utilize control parameters in the multicast messages tofacilitate corresponding transmission to the target location of apayload or other information included therein.

FIG. 2 illustrates a multicast protocol 18 having a sequence of messagesin accordance with one non-limiting aspect of the present invention tofacilitate multicast aided coordination. The sequence illustrates aplurality of messages 20, 22, 24, 26, 28, 30 being transmitted from thecentral coordination system to facilitate and aid in cooperativebeamforming as network conditions change over time. The multicastmessages may be broadcasted to all of the available remote antennaunits, e.g., to the five illustrate remote antenna units may each havecompleted the ranging process, or selectively to one or more remoteantenna units designated as members of a corresponding multicast group.The exemplary description herein presumes the multicast messages aretransmitted to each available remote antenna unit such that each remoteantenna unit within the distribution path receives the same multicastmessage. The remote antenna units would then individually identifywhether the message directs that remote antenna units to act inresponse. The information necessary for the remote antenna units todetermine whether to act in response may be entirely included within aheader of the messages, i.e., everything leftward of the payload. Theheaders may include control parameters sufficient for identifying theremote antenna units to transmit the payload and the delay, power orother adjustments needed for the payload transmissions (beams) to arrivein concert with identical payloads directed to the same target locationfrom other remote antenna units.

The illustrated messages exemplarily depict a unicast message 20 and aplurality of multicast message types 22, 24, 26, 28, 30. The unicastmessage 20 may be utilized to facilitate initialcommunication/authorizations with the target device in the eventmultiple remote antenna units are not expected to be used forfacilitating communications with the target access point or for othersituations when it may be undesirable to multicast the attendantinformation. The unicast message 20 may optionally ommit some or all ofthe contemplated control parameters as it may be unnecessary to utilizethe corresponding control parameters to synchronize operation with otherremote antenna units due to the unicast message optionally beingcontemplated for single source or non-coherent signaling. The multicastmessage types 22, 24, 26, 28, 30 are illustrated to depict ahypothetical sequence of events following use of the unicast message toinitially communicate with an end station whereafter multicast protocolsmay be employed to facilitate synchronizing multiple beams to addcoherently at the target location. The header of each of the multicastmessage types 22, 24, 26, 28, 30 may include the control parametersnecessary to synchronize signaling with each message including controlparameters sufficient for all of the remote antenna units intended totransmit the corresponding payload to the target location. Whilepredominately described with respect to the multicast message types 22,24, 26, 28, 30 including control parameters for each remote antenna unitintended for transmitting an included payload, individual messages orunicast messages may alternatively be employed to individuallycommunicate with remote antenna units such that multiple messages havingthe same payload but with different control parameters are transmittedto each of the one antenna units intended participate in the coherentbeamforming. Optionally, all remote antenna units that are part of themulticast group receive and manipulate the same multicast message. Whenfewer remote antenna units participate in the multicast group, themessage may be shorter such that this message grows or shrinks based onhow many are participating in this multicast group. Each remote antennaunit may only use the portion of the multicast message that pertains toit, in addition to the payload that is common to all remote antennaunits. A first or a second multicast message is not intended toreference a sequence and is rather intended to be a type of multicastmessage that is periodically sent until a change in the number ofparticipants in the multicast group occurs when a second type ofmulticast message occurs.

The control parameters may be positioned in the header betweenaddressing/routing information and the payload and are illustrated forexemplary purposes to include a remote antenna unit ID (R.Ant ID), abeam ID, a ΔT value, a ΔP value and a channel ID, however, additionalcontrol parameters and/or information may be similarly included withoutdeviating from the scope and contemplation of the present invention. Theremote antenna unit ID may be utilized to identify the individual remoteantenna unit associated with the control parameters, such as to providea mechanism for the remote continues to individually distinguish thecontrol parameters associated therewith. The beam ID may be utilized toidentify the beam or signal intended for transmitting the payload, suchas to enable the targeted end station to differentiate one beam fromanother. The ΔT value may represent a timing offset or differential ofthe associated remote antenna unit from the reference or index 0 antennaunit, such as to enable the corresponding remote antenna unit todetermine when it should transmit its signal for coherent arrival at thetarget location. The ΔP value may specify a power level, signalstrength, amplitude or other energy-related parameter of the signals tobe transmitted from the corresponding remote antenna unit, such as tofacilitate matching signal strength at the target location. The channelID may be utilized to identify a frequency band or individual channelover which the corresponding remote antenna unit is to transmit itssignaling. The payload may correspond with information, data or othermaterial desired to be wirelessly transmitted to the target location.

A first multicast message 22 may include a first set of controlparameters for defining wireless transmission of a first payload to thetarget end station. The first multicast message may correspond to a typeof control parameters when only one RAU is a member of the multicastgroup. This message type may repeat periodically until a change in themulticast group takes place, e.g., until an additional member is addedwhereupon the second type of multicast message 24 is used. The firstmessage 22 may correspond with a situation in which it is desirable fora single remote antenna unit or a multicast group with a single membercommunicating with the target end station, such as when loading or otheroperational demands limit the available remote antenna units and/or inthe event initial communications are necessary prior to additionalremote antenna units joining a multicast group. A second multicastmessage 24 may correspond with a joining operation where a second remoteantenna unit/member joins the first multicast group to form a secondmulticast group to communicate with the target end station, such as inresponse to the second remote antenna unit becoming available,operational demands requiring additional signaling or conditionsripening to permit coherent signaling at the target location. The secondmulticast message may include the first set of the control parametersused for the sole/first member of the first multicast group andadditionally a second set of control parameters for defining wirelesstransmissions from the second member of the second multicast group. Thesecond multicast message 24 may include a second payload fortransmission to the target end station from each of the members in thesecond multicast group, i.e., each of the first member and the secondmember wirelessly transmit the same, second payload (identicalinformation/data) to the target location to facilitate coherent additionof the two payloads.

A third multicast message 26 may be similar to the second multicastmessage 24 in so far as being used to add another remote antenna unitfor purposes of creating a third multicast group having three memberscapable of coherently communicating wireless signaling to the targetlocation. The third multicast message 26 may include a third set ofcontrol parameters for defining signaling of the newly added thirdmember to form a third multicast group. The third message may similarlyinclude a third payload for transmission to the target end station fromeach of the members in the third multicast group. A fourth multicastmessage 28 may correspond with a pruning operation where the thirdmember of the third multicast group may be removed to re-form the secondmulticast group or a new, fourth multicast group for purposes oftransmitting a fourth payload. The fourth multicast message 28 mayremove the control parameters for the third member of the thirdmulticast group, thereby effectively eliminating the third memberwithout having to notify the third member of its removal or otherwiseparticularly address messaging to it for purposes of instructing it toavoid transmission of the fourth payload. A fifth multicast message 30may be used for purposes of removing the first member from the fourthmulticast group to create a fifth multicast group for purposes oftransmitting a fifth payload to the target and station.

The coordination system may optionally continue to transmit additionalmulticast messages in the foregoing manner, optionally joining orpruning members to form new multicast groups as network conditionswarrant, to facilitate transport of different payloads to the target endstation. The central coordination system may operate in this manner togenerate various multicast messages for purposes of selectively addingand removing remote antenna units from multicast groups depending ondesired communication parameters, optionally adding or removing membersfrom the multicast groups by correspondingly adding or removing controlparameters from headers of the multicast messages. The identicality ofthe messages being received at the remote antenna units leveragescapabilities of multicast protocols to facilitate dissemination ofmatching payloads to a plurality of remote antenna units for purposes ofcoherently signaling the payload to the target location according tocontrol parameters individually specified for each member of thetransmitting, multicast group. Such one-to-many communications may bebeneficial in enabling members to be dynamically added and removed frommulticast groups by simply removing corresponding control parametersfrom headers of the related messaging. The central coordination systemmay generate the corresponding messages and optionally update orotherwise change the control parameters according to network variances,which may be dynamically determined through periodic ranging operations.

FIG. 3 illustrates a flowchart 34 of a method for synchronizing wirelesssignaling to coherently add and subtract at a target location inaccordance with one non-limiting aspect of the present invention. Themethod may be facilitated with the central coordination system, theremote antenna units, devices, etc. performing or executingcorresponding processes, such as according to functions and otherlogical operations related to processor execution of non-transitoryinstructions stored on a computer-readable medium. Block 34 relates todetermining remote antenna units (RAUs) available to facilitate clientcoherent signaling, which may include the central coordination systemdetermining each RAU capable of communicating therewith or each RAUdeployed within the overall communication system even if unable tospeaking with a particular target location. Block 36 relates todetermining data or other information, collectively referred to aspayload, desired for transmission to a target device or a targetlocation, e.g., multiple devices at one particular location. The methodis predominately described with respect to transmitting a singularpayload to a target location for exemplary purposes as the presentinvention fully contemplates leveraging its multicast capabilities tofacilitate transmission of multiple payloads, optionally simultaneously,to the same target location or multiple target locations using the sameor different remote antenna unit/multicast groups.

Block 40 relates to performing a ranging operation. The rangingoperation may relate to iteratively transmitting a test signal from eachof the available RAUs to determine those capable of reaching the targetlocation and/or pre-selecting from locational information or othersystem-level data the RAUs capable of communicating with the targetlocation, i.e., the RAUs capable of facilitating transmission of thepayload to the desired device(s). The ranging process may correspondwith iteratively transmitting signals from the RAUs according todifferent ranging parameters and assessing corresponding receipt at thetarget location until the attendant signaling is sufficient tofacilitate coherent addition and/or subtraction at the target location.The ranging parameters may be the same parameters as the controlparameters described above to facilitate controlling actual/real payloadtransmissions to the target location, e.g., the values of the rangingparameters may be iteratively changed until coherent signaling isachieved whereupon the last set of ranging values become the values forthe control parameters. The ranging parameters are described merely todifferentiate from the control parameters at least in that the rangingparameters are used to facilitate transmission of the test signal to thetarget location as opposed to transmission of the actual/real payload,i.e., transmission of information other than that determined in Blockfor transmission to the target location.

FIG. 4 illustrates test signaling 42 for the ranging process inaccordance with one non-limiting aspect of the present invention. Theranging process may include selecting a reference RAU as a baseline forcoordinating signaling of other RAUs to the target location. Thereference RAU may be indicated with an index of 0 with each of the otheravailable RAUs individually associated with a unique value greater than0 (RAU-0), which for exemplary purposes is illustrated with respect toone additional RAUs having an index value of 1 (RAU-1). The systemillustrated in FIG. 1 includes five RAUs and the ranging process may besimilarly performed for each of the five RAUs, and as such, theillustration is merely exemplary of processing contemplated by thepresent invention to facilitate determining control parameters necessaryfor facilitating coherent signaling at the target location. Transmissionof training signal 44, 46 from the RAUs may be facilitated with theabove-described multicast messages including a generic sinusoidal signalsegments with specific phase information as the payload, i.e., byinstructing through multicast messaging each RAU subjected to theranging process to transmit a sinusoidal signal according to rangingparameters included therein. The ranging process may be an iterativeprocess whereby multiple ranging messages may be multicasted to theavailable RAUs with correspondingly parameters sufficient to facilitatethe operations contemplated herein.

FIG. 4 illustrates a summation signal 48 being generated at the targetlocation according to test signaling 44, 46 emanating from RAU-1 theRAU-0 (reference RAU). The ranging parameters included in the attendantmulticast messaging may be selected by the coordination systemcontroller such that RAU-0 continuously transmits the sinusoidal signalwithout variation and RAU-1 begins to transmit a sinusoidal signal in amanner commensurate with RAU-0 and thereafter according to ΔT flips aphase of the sinusoidal signal 180°. The ΔT value used to instruct theRAU-1 when to flip the test signal becomes a known variable/value thatcan be used to assess a corresponding influence had the target location,which is shown to occur when the flipped, 180° out of phase signal fromRAU-1 cancels/subtracts the test signal from RAU-0 at the targetlocation from. FIG. 4 illustrates a segment of the test signal beingflipped by RAU-1 for exemplary purposes as the test signal may includeadditional segments for each of the other RAUs being tested to flipalong with corresponding instructions as to when those RAUs are to flipthe corresponding portion of the test signal. The target device or otherelement at the target location may responsively measure the summationsignal and communicate it or corresponding ranging results to thecoordination system controller with responsive messaging. Thecoordination system controller can then assess the results to determinewhen the ΔT value in the ranging parameters set for RAU-1 produced thezero signal or otherwise induced a subtraction in the summation signal,i.e., the coordination system controller can work backwards from the ΔTvalue in the summation signal to determine timing differences betweenthe signaling transmitted from RAU-0 and RAU-1.

The summation signal illustrates a complete cancellation within thesummation signal due to RAU-1 exactly flipping a corresponding testsegment of the sinusoidal signal in phase with the sinusoidal signalemanating from RAU-0. This may result from the coordination systemcontroller selecting an appropriate ΔT value within the initial rangingparameters associated with the test signal from RAU-1. One non-limitingaspect of the present invention contemplates a difficulty in initiallyselecting such a ΔT value, i.e., a ΔT value sufficient to initiallygenerate the complete cancellation, such that the processes associatedwith the ranging process may be iteratively performed according todifferent ΔT values for RAU-1 until the complete cancellation isachieved. The iterative process may include the coordination systemcontroller assessing non-zero signaling in the summation signal 48occurring relative to the ΔT value, i.e., when the RAU-1 was instructedto flip the sinusoidal signal segment, and based thereon, estimate orproject an increase or decrease in the ΔT value sufficient to facilitatetiming a flipping of the sinusoidal signal to occur in-phase with thetest signal emanating from RAU-0. The interferences, attenuation orother signaling influences on the test signals may be relatively unknownduring the ranging process such that the coordination system controllermay be required to iteratively increase/decrease the ΔT value until thedesired cancellation of the summation signal is achieved.

One non-limiting aspect of the present invention contemplates the RAU-1attempting to transmit its signal for a period of time (calibrationinterval) occurring prior to being flipped according to the ΔT value.This may be beneficial in enabling the RAU-1 to calibrate timing forprecisely determining when to flip the test signal. The summation signal48 is shown for illustrative purposes as coherently adding during thecalibration interval due to the illustrated ΔT value having produced acomplete cancellation of the summation signal. The summation signaloccurring during the calibration interval when the ΔT value fails toproduce a complete cancellation may result in the attendant signalinghaving a different waveform, amplitude or other characteristics thanthat being illustrated. Once the coordination system controllerdetermines a ΔT value sufficient for RAU-1 to produce the appropriatecancellation of the test signals from RAU-0 and RAU-1 at the targetlocation, the process may be iteratively repeated with each additionalRAU determined to be available in Block 36. The continued rangingprocess may include maintaining the ΔT value selected for RAU-1, i.e.,the ranging value sufficient to achieve the desired subtraction of thesignals from RAU-0 and RAU-1, with iterative variations in the rangingparameters for RAU-2 until the summation signal at the target locationfrom RAU-0, RAU-1 and RAU-2 produces a complete cancellation. This mayinclude the coordination system controller iteratively varying the ΔTvalue for RAU-2 until the desired cancellation is achieved. The processmay be repeated on a similar one-by-one basis for each additional RAUuntil ΔT values producing the desired cancellation are determined foreach available RAU.

Returning to FIG. 3, Block 52 relates to forming a multicast group tofacilitate multicasted transmission of the payload to a target locationfrom one or more RAUs. The multicast group may be formed by the centralcoordination system including control parameters for each of the groupmembers within the corresponding multicast messages. The centralcoordination system may decide which RAUs participate and for how longbased on a diversity on criteria that includes but is not limited totraffic, number of users, proximity to wireless end device, channelsavailable etc. Block 54 relates to multicasting the payload from theRAUs within the attendant multicast group until an entirety of thepayload is transmitted, e.g., multiple multicast messages may begenerated and transmitted before an entirety of the desired transmissionis completed. Dashed lines are illustrated to indicate optionalprocesses whereby the central coordination system may periodicallyperform the ranging operation while information determined in Block 38is still desired for transmission to the target location in order togenerate or double-check the ranging/control parameters previouslydetermined for purposes of assessing whether those parameters continueto be viable for coherent signaling as signaling conditions may changeor other influences may want adjustments. Additional dashed lines areillustrated indicate an optional process whereby the centralcoordination system periodically re-forms or prunes/joins members froman existing operational multicast group, such as to facilitateleveraging multicast protocol capabilities to seamlessly and dynamicallyat RAUs and/or remove RAUs from ongoing coherent indications at thetarget location.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A communication system having a plurality ofaccess points for transmitting wireless signaling to a target location,the system comprising: a central coordination system for identifyingcontrol parameters needed for two or more of the plurality of accesspoints to transmit a payload to the target location such that associatedwireless signaling coherently adds at the target location; wherein thecentral coordination system determines the control parameters as afunction of a ranging process, the ranging process including:determining one of the two or more of the plurality of access points asa reference access point; providing a test signal to the two or more ofthe plurality of access points; providing ranging parameters to the twoor more of the plurality of access points, the ranging parametersspecifying transmission of the test signal from the corresponding accesspoint to the target location; and iteratively varying the rangingparameters for the two or more of the access points other than thereference access point until the test signals transmitted therefromcancel at the target location with the test signals transmitted from thereference access point.
 2. The communication system of claim 1 whereinthe ranging parameters specify transmission of the test signals from thetwo or more of the access points other than the reference access pointto be out of phase relative to the test signals transmitted from thereference access point.
 3. The communication system of claim 1 whereinthe ranging parameters specify transmission of the test signals from thetwo or more of the access points to have matching waveforms.
 4. Thecommunication system of claim 1 wherein the central coordination systemcalculates a ΔT value as at least one of the ranging parameters for thetwo or more the plurality of access points, each ΔT value timingtransmission of the test signal from the corresponding access point tocancel with the test signal from the reference access point.
 5. Thecommunication system of claim 1 wherein the central coordination systemcalculates the ranging parameters to include a ΔP value for the two ormore of the plurality of access points, each ΔP value specifying powerfor transmission of the test signal from the corresponding access pointto facilitate cancellation of the corresponding wireless signaling atthe target location.
 6. The communication system of claim 1 wherein thecoordination system multicasts a message identifying the controlparameters for the two or more of the plurality of access points totransmit the payload such that wireless signaling associated therewithcoherently adds at the target location.
 7. The communication system ofclaim 6 wherein the coordination system multicasts the message to eachof the plurality of access points, the message omitting controlparameters for the access points other than the two or more of theplurality of access points.